A problem recently observed in connection with marine diesel engines, particularly those operating on low-sulphur marine diesel fuel, is that of liner lacquering whereby a hard resin-like material forms on cylinder liners and fills the honing grooves. This problem manifests itself in increased lubricating oil consumption which incurs a financial penalty. A solution to the problem, namely replacing the cylinder liners at regular intervals, also carries a financial penalty in that the vessel is temporarily out of commission during replacement of the liners in addition to the cost of replacement itself.
Initially it was thought that the problem was caused by deficiencies in engine design. Later the problem was ascribed to poor lubricating oil quality. The working pattern of the engine and the loads thereon were also thought to be contributory factors. However, a recent paper presented at the 20th International Congress of Combustion Engines, London, 1993, entitled `The Influence of Marine Fuel Quality On Lubricating Oil Performance` by R W Allen of Castrol International Marine presents a strong case for deteriorating marine diesel fuel quality being a major factor, together with engine overloading, in the occurrence of the problem. The paper makes the observation that gas oil sold into the marine market is in general of lower quality (higher boiling ranges end-point and higher aromatics content) and lower cost than that sold for automotive applications and concludes realistically that even though this type of fuel may be associated with the formation of liner lacquers in overloaded engines it will continue to be produced and sold because of its lower cost.
WO 97/44414 discloses that the problem can be significantly reduced by adding to the fuel a detergent and a combustion improver such as a cerium oxidic compound.